A suicide bomber has killed at least 50 people at a mosque in the north-eastern Nigerian town of Mubi, police say.

The teenage bomber detonated his explosives early on Tuesday in Adamawa state as people were arriving for morning prayers.

Police spokesman Othman Abubakar told AP the young man was mingling among the worshippers.

Eight people were critically injured and more than 30 others hurt were in a stable condition, said Idris Garga, the north-east regional coordinator for Nigeria's national emergency agency.

There was no immediate claim of responsibility, but the attack bears the hallmark of Boko Haram, which typically mounts suicide attacks in crowded public places, such as mosques and markets.

Last December, two schoolgirl suicide bombers killed 56 people and wounded dozens more at a market in Adamawa.

Tuesday's attack is the highest loss of life since 18 people were killed in neighbouring Borno state in September.

Boko Haram has waged an insurgency in north-east Nigeria since 2009 in its attempt to create an Islamic state in the region, killing more than 20,000 and forcing about 2 million people to flee their homes.

Most attacks by the group focus on Borno state, the birthplace of the insurgency.

The group held a swathe of land around the size of Belgium in Borno, Adamawa and Yobe states until early 2015, but were forced out by Nigeria's army backed by troops from neighbouring countries.

The group split in 2016 and the faction under Shekau is based in the Sambisa forest on the border with Cameroon and Chad and mainly targets civilians with suicide bombers.

The other faction is based in the Lake Chad region and is led by Abu Musab al-Barnawi to attack mainly military forces.

In a statement on Tuesday, Nigeria's President Muhammadu Buhari said the attack was "very cruel" and gave assurances his government would do "everything required" to secure the state from Boko Haram.